Knee replacement system and method for enabling natural knee movement

ABSTRACT

A method of implanting a knee replacement system in a leg with a femur and a tibia of a patient can include, implanting a femoral component onto a condyle of the femur and placing a trial tibial component on a tibial plateau of the tibia. The tension of a posterior cruciate ligament can be adjusted. The tension of an anterior cruciate ligament can be adjusted. The posterior position of the trial tibial component can be adjusted. The knee condition at toe off onset can be simulated during walking.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/185,730 filed on Jun. 15, 2010, which claims the benefit of U.S.Provisional Application Nos. 61/228,720, filed on Jul. 27, 2009 and61/307,070, filed on Feb. 23, 2010. The entire disclosures of each ofthe above applications are incorporated herein by reference.

FIELD

This invention relates generally to the knee arthroplasty field, andmore specifically to an improved knee replacement system for enablingnatural knee movement over a broad range of activities in the kneereplacement field.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Knee arthroplasty, in which the knee is partially or completely replacedwith a prosthetic knee, is a common surgical procedure performed torelieve pain or disability due to conditions such as osteoarthritis,rheumatoid arthritis and other forms of polyarthritis, cartilagedefects, meniscus tears, and ligament tears. Knee arthroplasty typicallyreplaces diseased or damaged joint surfaces of the knee, includingsurfaces on the femur, tibia and/or patella with artificial replacementcomponents made of metal or plastic parts designed to allow for kneemotion that is natural as possible. Natural knee motion is the result ofa complex relationship between primary movements of flexion-extensionand secondary movements of anterior-posterior translation andinternal-external rotation. This complex relationship defines afunctional envelope of motion, which varies from activity to activity.

Current knee replacement systems are unable to facilitate naturalfunctional envelopes of motion, fail to engage the anterior andposterior cruciate ligaments and are therefore less-than-ideal forenabling natural knee movement over a wide range of activities of dailyliving. Current knee replacement systems also typically limit theactivities of patients with knee replacements, and do not address thehigh performance needs and desires of younger or more active agingpatients who typically participate in higher impact activities such asrunning.

Thus, there is a need in the knee replacement field to create animproved knee replacement system that facilitates natural knee movementover a broad range of activities. This invention provides such animproved knee replacement system

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

A method of implanting a knee replacement system in a leg with a femurand a tibia of a patient can include, implanting a femoral componentonto a condyle of the femur and placing a trial tibial component on atibial plateau of the tibia. The tension of a posterior cruciateligament can be adjusted. The tension of an anterior cruciate ligamentcan be adjusted. The posterior position of the trial tibial componentcan be adjusted. The knee condition at toe off onset can be simulatedduring walking. The anterior position of the trial tibial component canbe adjusted such that the posterior cruciate ligament in the leg resiststhe simulated toe off knee condition. A position of the trial tibialcomponent at the adjusted posterior and anterior positions can bemarked. A tibial component can be implanted onto the tibial plateau inthe patient in the marked position that articulates with the femoralcomponent.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a schematic unfolded view of the preferred embodiment of theknee replacement system;

FIG. 2 is a side view of a femoral component articulating with a tibialcomponent of the preferred embodiment;

FIGS. 3A, 3B, and 3C are unfolded views of the medial tibial componentand the lateral tibial component of the preferred embodiment in neutralstance, heel strike phase, and toe off phase, respectively;

FIGS. 4A, 4B, and 4C are unfolded views of the medial tibial componentand the lateral tibial component of the preferred embodiment in neutralstance, flexion during stair climbing, and deep flexion, respectively;

FIGS. 5A and 5B are a sagittal view and frontal cross section view,respectively, of an example articulation between the medial femoralcomponent and the medial tibial component of the preferred embodiment;

FIGS. 6A and 6B are a sagittal view and frontal cross section view,respectively, of an example articulation between the lateral femoralcomponent and the lateral tibial component of the preferred embodiment;

FIGS. 7A and 7B are sagittal views of the medial femoral componentarticulating with the medial tibial component and of the lateral femoralcomponent articulating with the lateral tibial component, respectively,in the preferred embodiment;

FIGS. 8A and 8B are sagittal view schematics of the medial functionalenvelope of motion and the lateral functional envelope of motion;

FIG. 9A is a superior view schematic of the medial and lateral tibialcomponents of the preferred embodiment implanted on a tibia;

FIG. 9B is a view of frontal cross-sections of the medial and lateraltibial components, taken along the lines A-A through A-F of FIG. 9A,shown articulating with the medial and lateral femoral components,respectively;

FIG. 10A is an inferior view schematic of the medial and lateral femoralcomponents of the preferred embodiment implanted on a femur, withselected frontal cross sections of the medial and lateral femoralcomponents;

FIG. 10B is a view of frontal cross-sections of the medial and lateralfemoral components, taken along the lines B-A through B-F of FIG. 10A;

FIGS. 11A and 11B are sagittal views of example embodiments of themedial and lateral femoral components, respectively;

FIGS. 11C and 11D are frontal cross-section views of example embodimentsof the medial and lateral femoral components, respectively;

FIG. 11E is an inferior view of example embodiments of the medial andlateral femoral components, implanted on the medial and lateralcondyles, respectively, of a femur;

FIGS. 12A, 12B, and 12C are schematics of the steps of adjusting theposterior position of the medial tibial component, adjusting theanterior restraint of the lateral and medial tibial components, andadjusting the posterior position of the lateral tibial component,respectively, of the preferred embodiment;

FIG. 13 is a table schematically illustrating several example modes inwhich a selected portion of the components of the system of thepreferred embodiment may be implanted;

FIG. 14 is a flowchart of the preferred method for implanting the kneesystem of the preferred embodiment;

FIG. 15 is a flowchart detailing the step of placing a trial tibialcomponent;

FIG. 16 is a flowchart detailing the step of adjusting the posteriorposition of the trial tibial component;

FIG. 17 is a flowchart detailing the step of adjusting the anteriorposition of the trial tibial component; and

FIGS. 18A-18D are schematics of a full femoral component, a medialpartial femoral component, a lateral partial femoral component, and afull tibial component, respectively, of a preferred embodiment.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

The following description of preferred embodiments of the invention isnot intended to limit the invention to these preferred embodiments, butrather to enable any person skilled in the art to make and use thisinvention. In the following description, unless otherwise stated, theterms “proximal”, “distal”, “medial” and “lateral” are used relative tothe midline of a person.

1. Knee Replacement System for Enabling Natural Knee Movement

As shown in FIG. 1, the knee replacement system 100 preferably includesa medial femoral component 110, a medial tibial component 130, a lateralfemoral component 150, a lateral tibial component 170, and a patellarflange component 190. The knee replacement system 100 may furtherinclude a patellar component. In an alternative embodiment, the medialfemoral component 110, lateral femoral component 150, and/or patellarflange component 190 may be integrated into a full femoral component ora partial femoral component of unitary construction. Similarly, inanother alternative embodiment, the medial tibial component 130 andlateral tibial component 170 may be integrated into a full tibialcomponent of unitary construction. As shown in FIG. 13, the kneereplacement system 100 is preferably modular and may be used in multiplemodes, such that a selected portion or all of the components may beimplanted in any combination in a patient, depending on the needs of thepatient. In one example of a mode, only the medial femoral component 110and the medial tibial component 130 may be implanted in a patient whohas degradation in only the medial compartment of their knee. In anotherexample of a mode, all components may be implanted in a patient whorequires a total knee replacement. Furthermore, modular components allowany individual component to be customized for a patient if needed,without requiring the entire system to be customized.

The knee replacement system 100 preferably enables a range of kneemotion having the following characteristics: (1) Hyperextension of up toapproximately −15 to −20 degrees; (2) At full extension (leg angle of 0degrees), the leg may undergo external rotation of approximately 10 to15 degrees and internal rotation of approximately 10 to 15 degrees; (3)At moderate flexion (leg angle of approximately 20 to 30 degrees), theleg may undergo external rotation of up to approximately 15 degrees andinternal rotation of up to −15 degrees; (4) At higher flexion (leg angleof 120 degrees or more), the leg may undergo external rotation ofbetween approximately 25 and 30 degrees with posterior translation ofthe lateral tibial component; and (5) Deep flexion of up toapproximately 145 degrees. The knee replacement system 100 is designedto enable natural knee motion by facilitating natural envelopes offunctional motion (EFMs), such as the EFM 105 shown in FIG. 2, thatdescribe possible ranges of translational motions between thearticulating surfaces of the femur and the tibia over a broad range ofactivities, and by allowing motion between medial components to bedifferent from lateral components. As shown in FIGS. 3 and 4, naturalEFMs include a medial EFM 107 defined between an anterior range 107′ anda posterior range 107″, and a lateral EFM 109 defined between ananterior range 109′ and a posterior range 109″. The medial EFM 107 isthe range of movement at the articular surface between the medial sidesof the femur and tibia. Similarly, the lateral EFM 109 is the range ofmovement at the articular surface between the lateral sides of the femurand tibia. The knee replacement system 100 preferably facilitatesnatural EFMs by permitting a range of movement, including differentmedial side and lateral side component motion, at the articular surfacebetween the femur and the tibia of the knee joint when the knee flexesat particular key flexion angles. The EFMs provided by the kneereplacement system 100 preferably change as the knee flexes at these keyflexion angles. The knee replacement system preferably furtherfacilitates natural EFMs by incorporating the anterior and posteriorcruciate ligaments, which are preferably tensioned at specified kneeflexion angles during implantation of the knee replacement system.

In one embodiment, the knee replacement system 100 preferably defines amedial EFM 107 based on the amount of anterior-posterior translation andinternal-external rotation that the knee undergoes during walking,stair-climbing and deep flexion as a function of knee flexion angle. TheEFMs based on these activities preferably also cover the range of EFMsfor a broader range of daily activities such as running or rising from achair. As an example, as shown in FIG. 3, the anterior range 107′ andposterior range 107″ of the medial EFM for walking are a result of therelative positions of the articulating surfaces of the medial femoralcomponent 110 and the medial tibial component 130 during the toe off andheel strike phases, respectively, of the walking gait cycle. The rangeof movement that naturally occurs when the knee is sustaining highcompressive loads, such as during walking, squatting and otheractivities may further define the medial EFM.

Similar to the medial EFM 107, the knee replacement system preferablydefines a lateral EFM 109 based on the amount of internal and externalrotation that the knee undergoes during walking and deep flexion as afunction of knee flexion angle. As an example, as shown in FIG. 3C, theanterior range 109′ of the lateral EFM for walking is a result of therelative positions of the articulating surfaces of lateral femoralcomponent 150 and the lateral tibial component 170 during the toe offphase of the walking gait cycle. As shown in FIG. 4C, the posteriorrange of the lateral EFM for walking is a result of the relativepositions of the lateral femoral component 150 and the lateral tibialcomponent 170 during activities involving deep flexion, such as stairclimbing and squatting. The range of movement that naturally occurs whenthe knee is sustaining high compressive loads, such as during walking,squatting and other activities, may further define the lateral EFM. Themedial EFM 107 and lateral EFM 109 are preferably different from eachother to allow uncoupled medial component and lateral component motions,which better emulates natural EFMs.

The medial and lateral EFMs are preferably further based on theincorporation of the cruciate ligaments. As one ordinarily skilled inthe art will recognize, the anterior cruciate ligament (ACL) 103 and theposterior cruciate ligament (PCL) 101 normally function together toprovide mobility and stability within the conditions defined by themedial and lateral EFMs. The anterior and posterior ranges of the EFMsare preferably adjusted such that the anterior and posterior constraintsto motion are provided by the ACL 103 and PCL 101, and not the physicalconstraints of the articular surfaces of the femoral and tibialcomponents. The posterior constraint of the medial EFM is preferablydetermined with the knee at full extension and the tibia anteriorlydisplaced and externally rotated, as shown in FIG. 12A. The anteriorranges of the medial and the lateral EFMs are preferably determined withthe knee at full extension and the tibia posteriorly displaced andinternally rotated, as shown in FIG. 12B. The posterior constraint ofthe lateral EFM is preferably determined with the knee in deep flexionand the tibia internally rotated, as shown in FIG. 12C.

The medial femoral component 110 of the knee replacement systemfunctions to provide a bearing surface on the medial condyle of thefemur. As shown in FIG. 1, the medial femoral component 110 ispreferably implantable on the medial condyle on the distal end of thefemur, and preferably includes a medial femoral articulating surface 112that articulates with the medial tibial articulating surface 132 of themedial tibial component 130 throughout knee movement. As shown in FIGS.1 and 10A, the medial femoral component 110 preferably covers andintegrates with the medial condyle, and preferably includes an internalcurvature to conform to the natural surface of the medial condyle.However, the medial femoral component 110 may alternatively have anysuitable shape to conform to any suitable surface, including a condylesurface that is surgically manipulated to mate with the medial femoralcomponent 110. The frontal plane profile of the medial femoralarticulating surface 112 preferably includes a blended radius, which mayhelp reduce stress concentrations. The medial femoral component 110 ispreferably one of a size selected from a group of available sizes, butmay alternatively be a customized size and/or include customizedfeatures for a patient. As shown in FIG. 5B, the articulating surface ofthe medial femoral component 110 preferably includes a broad exteriorcurvature in the frontal plane, which minimizes contact stress bydistributing force across the broad contact surface and permits slidingand rotation between the articulating surface. The radius of curvatureof the medial femoral component 110 at the articulating points ofcontact with the medial tibial component 130 preferably varies with legflexion angle, such that a specified range of articular motion occurs atkey flexion angles. For example, the radius of curvature in the medialfemoral component at the articulating point of contact between themedial femoral and medial tibial components for near full extensionduring walking is different than that for 45 degrees of flexion duringstair climbing. As shown in FIG. 7A, the sagittal profile of the medialfemoral articulating surface of the medial femoral component 110 ispreferably defined by four medial femoral arcuate portions (a superior,a posterior, a distal, and an anterior medial femoral arcuate portions)and a scaling factor 126 measuring the offset from the posterior edge ofthe medial condyle in the central sagittal plane of the medial femoralcomponent 110. The superior, posterior, distal, and anterior arcuateportions preferably have medial radii of curvature of a superior radius121, posterior radius 120, a distal radius 122, and an anterior radius124, respectively. The medial radii of curvature preferably originatefrom distinct arc centers, but may alternatively originate from anysuitable points in the sagittal plane profile of the medial femoralcomponent 110. The medial femoral arcuate portions are preferablydesigned based on anatomical measurements needed to provide the medialand lateral EFMs. As shown in FIG. 7A, the distal medial femoral arcuateportion preferably sweeps a greater angle than each of the posterior andanterior medial femoral arcuate portions, and preferably sweeps the sumof a posterior angle 116 and an anterior angle 118. The distal radius ofcurvature 122 is preferably longer than the posterior and anterior radiiof curvature 120 and 124, respectively, and the relative lengths of thefour medial radii of curvature 121, 120, 122 and 124 are preferablyconstant over the group of available sizes of the medial femoralcomponent 110. Each of the group of available sizes of medial femoralcomponents is preferably sized to the scaling factor 126. However, themedial femoral component may alternatively have any exterior shape thatis suitable for articulating with the medial tibial component or naturaltibial plateau. As shown in FIG. 10A, a central line (defined as theline extending from the midline of the posterior edge of the component110 along the midline of the component width) in an inferior view of thecomponent is preferably at an angle 128, and the exact angle measurementmay depend on anatomy of the patient.

The medial femoral component 110 is preferably made of a biocompatiblemetal, such as zirconium, titanium, chromium, cobalt, molybdenum, and/orany suitable material, using milling, casting, sanding, polishing and/orother suitable manufacturing and finishing processes. The medial femoralcomponent 110 is preferably implanted on the surface of the medialfemoral condyle of a patient using biological fixation, other fixativessuch as bone cement, or through any suitable method known and used byone skilled in the art, such as that described in U.S. Pat. No.5,171,244, entitled, “Methods and apparatus for arthroscopic prostheticknee replacement”, which is incorporated in its entirety by thisreference. Prior to implantation, the medial condyle may be preparedwith a sequence of cuts, including a distal cut preferably perpendicularto the neutral axis of the femur, anterior and posterior cuts, andchamfer cuts to complement the internal curvature or surface of themedial femoral component 110. These cuts may be made with the aid ofjigs, instrumented tools, robotics or other devices to improve theaccuracy of the cuts, and to improve the consistency of theinterdependence between components of the knee replacement system. Thesematerials and processes of manufacture and implantation are known andused in the art of knee replacement systems and other implanted devices,and their implementation would be readily understood by one ordinarilyskilled in the art of knee replacement systems.

The medial tibial component 130 of the knee replacement system functionsto provide a bearing surface on the medial tibial plateau of the tibia.As shown in FIGS. 1 and 9A, the medial tibial component 130 isimplantable on the medial tibial plateau of the proximal end of thetibia and includes a medial tibial articulating surface 132 thatpreferably articulates with the medial femoral articulating surface 112of the medial femoral component 110 throughout knee movement. The medialtibial component 130 preferably is implanted on the proximal end of thetibia, by attaching to a medial base plate that is fixated to asurgically-prepared proximal tibial plateau surface with biologicalfixation, bone cement, or another suitable fixative. However, the medialtibial component may alternatively be implanted directly to asurgically-prepared medial tibial plateau surface, similar to the medialfemoral component 110. Prior to implantation of the medial tibialcomponent, the medial tibial plateau is preferably prepared with asequence of cuts including a distal cut preferably perpendicular to theneutral axis of the tibia, and medial and lateral cuts having equalposterior slopes to facilitate proper function of the PCL and ACL. Thesecuts may be performed with a jig, instrumented tools, robotics or otherdevices to improve accuracy of the desired cuts and to improve theconsistency of the interdependence between components of the kneereplacement system. Where both the medial and lateral tibial componentsare implanted, the intercondylar eminence space between the medial andlateral tibial plateaus is preferably equal to or narrower than thewidth of the spacing between the medial and lateral femoral condyles, tofacilitate proper articulation between the femur and tibia. The medialtibial component 130 is preferably implanted such that the bottomsurface (the distal surface) is at an angle 148 relative to thehorizontal. The exact measurement of angle 148 preferably depends on theanatomy of the patient. The angle 148 is preferably introduced byimplanting the medial tibial component 130 in a sloped cut, but mayalternatively be built into the medial tibial component 130 to allow ahorizontal, neutral cut. As shown in FIGS. 8A and 9A, the medial tibialarticulating surface 132 preferably includes a broad, nearly flatplateau surface in the sagittal and frontal planes that articulates withthe medial femoral articulating surface 112 of the medial femoralcomponent 110. Like that of the medial femoral component, thearticulating surface 132 of the medial tibial component 130 preferablyminimizes contact stress by distributing force across the broad contactsurface and minimizes rotational restraint. Furthermore, similar to themedial femoral component 110, the radius of curvature of the medialtibial component 130 at the articulating points of contact between themedial tibial and the medial femoral components preferably varies withleg flexion angle, such that a specified range of articular motionoccurs at key flexion angles. The medial tibial component 130 preferablyincludes a thickness and tibial plane coverage size that are selectedfrom a group of available thicknesses and sizes based on the specificneeds of the patient. For example, a petite patient may require athinner and/or smaller planar sized medial tibial component than alarger patient. As shown in FIG. 8A, the sagittal profile of the medialtibial component 130 is preferably defined by two medial tibial arcuateportions (a posterior and an anterior medial tibial arcuate portions)and a scaling factor 144 measuring the medial EFM. The posterior andanterior medial tibial arcuate portions preferably have medial radii of140 and 142, respectively. The medial tibial arcuate portions arepreferably designed with considerations similar to those for thesagittal profile of the medial femoral component 110, but for varioussizes of the medial tibial component 130. The medial radii of curvature,thickness, size, specific placement, and/or other geometry of the medialtibial component may be further adjusted to facilitate specific ACL andPCL function by inducing different ranges of EFMs.

As shown in FIGS. 9A and 9B, the most medial portion (relative to themidline of the tibia) of the medial tibial component 130 preferablyincludes a raised edge 146 that functions to constrain medial-lateralmotion between the femur and the knee. The raised edge preferably slopesto a plateau with a curvature that complements the medial side of themedial femoral component 110. As shown in FIGS. 9A and 9B, the raisededge 146 preferably increases in width as it approaches in an anteriordirection and wraps around the anterior side of the medial tibialcomponent 130.

The medial tibial component 130 is preferably made of a durable,wear-resistant, shock-absorbent biocompatible material, such asultra-high molecular weight polyethylene. In an alternative version, themedial tibial component 130 is made of multiple materials such thatdifferent areas of the medial tibial component are optimized fordifferent mechanical demands. As shown in FIG. 2, the anterior region145′ and posterior region 145 of the medial tibial component may be madeof a material that is ideal for resisting fracture from impacts, and/orthe central region 147 may be made of a material that is ideal forresisting adhesion and repeated abrasive wear. The medial tibialcomponent 130 is preferably manufactured in a milling, casting,injection molding, sanding, polishing, and/or any other suitablemanufacturing and finishing processes.

To achieve a natural medial EFM 107, the medial tibial component 130 ispreferably implanted in a patient such that the anterior cruciateligament (ACL) 103 and the posterior cruciate ligament (PCL) 101function as they normally do in a healthy knee. In a healthy knee, asthe knee reaches full leg extension there is anterior displacement andexternal rotation of the tibia (such as at onset of heel strike duringwalking). These motions load the ACL in tension, which allows the ACL toguide the anterior and external rotational motion of the tibia. In asimple leg extension test, an assessment of the tibial translation andexternal rotation as the leg extends may be performed tointraoperatively evaluate ACL function. Similarly, in a healthy knee, asthe knee flexes to approximately 45 degrees, the PCL is in tension,which provides the posterior translation of the femur relative to thetibia during activities such as stair climbing. An iterative approachinvolving simulating heel strike and toe off with trial component sizesis preferably performed to select the appropriate size component andposition the component, such that constraint of anterior-posteriormotion of the component is similar to that in a healthy knee. An initialtrial component size is preferably mounted on a fixture that permitsanterior-posterior adjustment of the component, and the fixture istemporarily placed on the medial tibial plateau. Once the suitable sizeand anterior-posterior position of the trial component are found, theposition is preferably marked and used to appropriately position amedial tibial component 130 for implantation. Adjustment of the medialtibial component may be performed at the same time as adjustment of thelateral tibial component 170, or may be performed iteratively insuccession with adjustment of the lateral tibial component.

To adjust the posterior constraint of the medial tibial component 130,the size and/or anterior-posterior position of the component arepreferably iteratively adjusted until ACL tension resists combined legmotions that simulate the natural knee conditions at onset of heelstrike during walking. To adjust the anterior constraint of the medialtibial component, the size and/or anterior-posterior position arepreferably iteratively adjusted until PCL tension resists combined legmotions that simulate the natural knee conditions at toe off duringwalking. When the tension of the ACL and/or the PCL resist these motionsbefore the conflicting geometries of the medial femoral component 110and the medial tibial component 130 resist these motions, the kneemedial tibial component is appropriately positioned.

The lateral femoral component 150 of the knee replacement systemfunctions to provide a bearing surface on the lateral condyle of thefemur. As shown in FIG. 1, the lateral femoral component is preferablyimplantable on the lateral condyle on the distal end of the femur andpreferably includes a lateral femoral articulating surface that 152articulates with the lateral tibial articulating surface 172 of thelateral tibial component 170 throughout knee movement. The lateralfemoral component 150 preferably covers and integrates with the lateralcondyle located on the distal end of the femur. Except as noted below,the general geometry of the lateral femoral component 150 is preferablysimilar to that of the medial femoral component 110. The specific localradii of curvature of the lateral femoral component 150 are designed forthe lateral side of the knee, as shown in FIG. 7B. As shown in FIG. 7B,the sagittal profile of the lateral femoral articulating surface 152 ispreferably defined by four lateral femoral arcuate portions (a superior,a posterior, a distal, and an anterior lateral femoral arcuate portion)and a scaling factor 166 measuring the offset from the posterior edge ofthe lateral condyle in the central sagittal plane of the lateral femoralcomponent 150. The superior, posterior, distal, and anterior arcuateportions preferably have radii of curvature of a superior radius 161, aposterior radius 160, a distal radius 162, and an anterior radius 164,respectively, which are designed with considerations similar to thosefor the sagittal profile of the medial femoral component 110, but forvarious sizes of the lateral femoral component. The posterior, distal,and anterior radii of curvature of the lateral femoral component 150 maybe different from that of the medial femoral component 110, for example,to accommodate anatomical differences between the medial and lateralsides of the knee. For example, the anterior and the distal lateralfemoral radii of curvature 164 and 162 may be longer than the anteriorand the distal medial femoral radii of curvature 124 and 122,respectively. As shown in FIG. 7B, the distal lateral femoral arcuateportion preferably sweeps the sum of a posterior angle 156 and ananterior angle 158. The lateral femoral component 150 is preferably madeof the same material as the medial femoral component 110, and ispreferably manufactured and implanted in a patient in a manner similarto that of the medial femoral component. However, the preparation of thelateral femoral condyle prior to implantation of the lateral femoralcomponent is preferably coupled to the preparation of the medial femoralcondyle, to preserve interdependence between components of the kneereplacement system. The proper interdependence may be attained with, forexample, the use of a jig, robot, instrumentation, or other guide.

The lateral tibial component 170 functions to provide a bearing surfaceon the lateral tibial plateau of the tibia. As shown in FIG. 1, thelateral tibial component 170 is preferably implantable on the lateraltibial plateau on the proximal end of the tibia, and includes a lateraltibial articulating surface that preferably articulates with the lateralfemoral component 150 throughout knee movement. The lateral tibialcomponent 170 is preferably implanted on the proximal end of the tibia,by attaching to a lateral base plate that is fixated to asurgically-prepared proximal tibial plateau surface with biologicalfixation, bone cement, or another suitable fixative. However, thelateral tibial component 170 may alternatively be implanted directly toa surgically-prepared lateral tibial plateau surface, similar to themedial tibial component 130. Like the medial tibial component 130, thelateral tibial component 170 is preferably implanted such that thebottom surface (the distal surface) is at an angle 188 relative to thehorizontal. The exact measurement of angle 188 preferably depends on theanatomy of the patient. The angle 188 is preferably introduced byimplanting the lateral tibial component 130 in a sloped cut, but mayalternatively be built into the lateral tibial component 130 to allow ahorizontal, neutral cut. As shown in FIGS. 9A and 9B, the generalgeometry of the lateral tibial component 170 is preferably similar tothat of the medial tibial component 130, including a medial raised edge186, except that the specific local radii of curvature are designed forthe lateral side of the knee, as shown in FIG. 8B. As shown in FIG. 8B,the sagittal profile of the lateral tibial component 170 is preferablydefined by two lateral arcuate portions (a posterior and an anteriorlateral tibial arcuate portions) and a scaling factor 184 measuring thelateral EFM. The posterior and anterior arcuate portions preferably havelateral radii of curvature 180 and 182, respectively. The posterior andanterior lateral tibial arcuate portions are preferably designed withconsiderations similar to those for the sagittal profile of the medialtibial component 130, but for various sizes of the lateral tibialcomponent 170. The lateral tibial component is preferably made of thesame material as the medial tibial component, and is preferablymanufactured in a manner similar to that of the medial tibial component.

To achieve a natural lateral EFM, the lateral tibial component 170 ispreferably implanted in a patient such that the PCL and the ACL functionas they normally do in a healthy knee. In a healthy knee, deep legflexion and internal rotation of the tibia (such as during squatting) ispermitted by the PCL. In a healthy knee, nearly full leg extension withposterior displacement and internal rotation of the tibia (such as atonset of toe off during walking) loads the PCL in maximum tension, whichallows the PCL to restrict posterior motion of the tibia. An iterativeapproach involving simulating squatting and toe off with trial componentsizes is preferably performed to select the appropriate size componentand position the component, such that constraint of anterior-posteriormotion of the component is similar to that in a healthy knee. An initialtrial component size is preferably mounted on a fixture that permitsanterior-posterior adjustment of the component, and the fixture istemporarily placed on the medial tibial plateau. Once the suitable sizeand anterior-posterior position of the trial component are found, theposition is preferably marked and used to appropriately position amedial tibial component 130 for implantation. Adjustment of the lateraltibial component may be performed at the same time as adjustment of themedial tibial component, or may be performed iteratively in successionwith adjustment of the medial tibial component.

To adjust the posterior constraint of the lateral tibial component 170,the size and/or anterior-posterior position of the component arepreferably iteratively adjusted until PCL tension permits leg motionsthat simulate the natural knee conditions during squatting. Adjustmentof the anterior constraint of the lateral tibial component 170 ispreferably identical to that of the medial tibial component 130. Whenslack of the PCL permits simulated squatting and the tension of the ACLresists simulated toe off before the conflicting geometries of themedial femoral component 110 and the medial tibial component 130 resistsimulated toe off, the lateral tibial component 170 is appropriatelypositioned.

The patellar flange component 190 preferably functions to provide acontacting surface for the patella. As shown in FIG. 1, the patellarflange component 190 preferably attaches to the anterior distal portionof the femur, replacing or enhancing the anterior portion of thearticular cartilage. The patellar flange 190 is preferably made of thesame material as the medial and/or lateral femoral component, but mayalternatively be made of any suitable material. The patellar flangecomponent is preferably implanted on the femur with biological fixation,bone cement, or another suitable fixative in a manner similar to themedial and lateral femoral components. The patellar flange is preferablymanufactured in a milling, casting, injection molding, sanding,polishing, and/or any suitable manufacturing and finishing processes, asknown to one ordinarily skilled in the art of knee replacement systems.

In a second preferred embodiment of the system, as shown in FIG. 18A,the system includes a full femoral component 310. The full femoralcomponent 310 preferably includes the medial femoral component 110, thelateral femoral component 150, and the patellar flange component 190integrated into one piece. In variations of this alternative embodiment,the system includes a medial partial femoral component 312 that includesthe medial femoral component 110 and the patellar flange component 190integrated into one piece (FIG. 18B), or a lateral partial femoralcomponent 314 that includes the lateral femoral component 150 and thepatellar flange component 190 integrated into one piece (FIG. 18C).Alternatively, the partial femoral components 312 and 314 may eachinclude only a portion of the patellar flange component; for example,the medial partial femoral component 312 may include the medial half ofthe patellar flange component. The relative positions of the individualcomponent portions within each of the full and partial femoralcomponents are preferably substantially fixed, but may be slightlyadjustable (for example, due to compliance in the material).

In a third alternative embodiment of the system, as shown in FIG. 18D,the system includes a full tibial component 320. The full tibialcomponent 320 preferably includes the medial tibial component 130 andthe lateral tibial component 170. As shown in FIG. 18D, the medial andlateral tibial components are preferably joined by a bridge 322 adaptedto cross the anterior space between the medial and lateral tibialplateaus when the full tibial component 320 is implanted in a patient.However, the bridge 322 may additionally and/or alternatively join themedial and lateral tibial pieces at any location. The bridge 322functions to secure the relative positions of the medial and tibialcomponents. The bridge 322 is preferably slightly concave, curvingdistally towards the tibia when implanted, but may be flat or have anysuitable profile. The bridge 322 is preferably one connection joiningthe medial and lateral tibial components, but may alternatively includemultiple connections that join the medial and lateral tibial components,such as in a parallel, criss-cross, and/or web-like manner. However, thebridge 322 may be any suitable shape. Similar to the full and partialfemoral components, the relative positions of the medial and tibialcomponents in the full tibial component are preferably substantiallyfixed, but may be slightly adjustable (for example, due to compliance inthe material).

In other alternative embodiments of the system, the system includes apatellar surface replacement. The patellar surface replacement functionsto provide a replacement of the patellar surface that articulates withthe femur. The patellar surface replacement is preferably made of amaterial similar to the medial and lateral tibial components, andimplanted on the patella in a manner similar to the medial and lateralfemoral components. The system may also include a patellar component toreplace the entire patella and articulate with the femur.

One specific, exemplary embodiment of the system is shown in FIG. 11.The shown dimensions (which include various angles, radii of curvature,and other dimensions defining the geometry of the medial femoralcomponent, medial tibial component, lateral femoral component, andlateral tibial component) that are designed for an average sizeCaucasian male.

2. Method of Supplying a Knee Replacement System for Implantation

As shown in FIG. 13, in a preferred embodiment, the method 400 ofsupplying a knee replacement system for implantation in a patientincludes the steps of: providing a set of multiple medial femoralcomponents, providing a set of multiple lateral femoral components,providing a set of multiple full femoral components, providing a set ofmultiple partial femoral components, providing a set of multiple medialtibial components, providing a set of multiple lateral tibialcomponents, and providing a set of multiple full tibial components. Themethod may further include providing at least one patellar flangecomponent, providing at least one patellar surface replacementcomponent, and/or providing a patellar component. The medial femoralcomponents, lateral femoral components, full and partial femoralcomponents, medial tibial components, lateral tibial components, fulltibial components, patellar flange components, patellar surfacereplacement components, and patellar components are preferably similarto those described above in Section 1.

In a first variation of the method, the method further includes thesteps of selecting a medial femoral component from the set of multiplemedial femoral components, and/or selecting a medial tibial componentfrom the set of multiple medial tibial components. The selection may bebased on consideration of at least one of multiple factors, includinggender, patient height, patient weight, degree and type of kneedegeneration, and/or any suitable factor. For instance, smallercomponents (femoral and tibial components scaled to a smaller scalingfactor) may be more appropriate for a smaller patient. As anotherexample, the steps of selecting a medial femoral component and selectinga medial tibial component may be performed for implantation of the kneesystem in a patient with degeneration on only the medial side of theknee.

In a second variation of the method, the method further includes thesteps of selecting a lateral femoral component from the set of multiplelateral femoral components and a lateral tibial component from the setof multiple lateral tibial components. The second variation of themethod is preferably similar to the first variation of the method,except the second variation of the method incorporates lateral sidecomponents of the knee system.

In a third variation of the method, the method further includes the stepof selecting a full femoral component from the set of multiple fullfemoral components. Similarly, in a fourth variation of the method, themethod further includes the step of selecting a full tibial componentfrom the set of multiple full tibial components. The third and fourthvariations are preferably similar to the first variation of the method,except the full femoral component incorporates both the medial andlateral side femoral components of the knee system, and the full tibialcomponent incorporates both the medial and lateral side tibialcomponents of the knee system.

In a fifth variation of the method, the method further includes thesteps of selecting a medial partial femoral component or a lateralpartial femoral component from the set of multiple partial femoralcomponents. The fifth variation is preferably similar to the firstvariation of the method, except the fifth variation incorporates amedial partial femoral component (including a medial femoral componentand at least a portion of the patellar flange component) or a lateralpartial femoral component (including a lateral femoral component and atleast a portion of the patellar flange component).

The method of supplying a knee replacement system includes everycombination and permutation of the above described steps. As shown inFIG. 13, components of the knee replacement system may be implanted indifferent combinations in different “modes”.

3. Method of Implanting a Knee Replacement System

As shown in FIG. 14, the method 200 of implanting the knee replacementsystem in a leg of a patient includes the steps of implanting a femoralcomponent onto a condyle of a femur in the leg S210, placing a trialtibial component on a tibial plateau of a tibia in the patient S220,adjusting at least one of tension of a cruciate ligament and position ofthe trial tibial component S240, verifying appropriate cruciate ligamenttension and trial tibial component position S270, marking the positionof the trial tibial component S280, and implanting a tibial component inthe patient in the marked position S290.

The step of implanting a femoral component S210 is well known by oneordinarily skilled in the art. In a first variation, the step ofimplanting a femoral component includes implanting a medial femoralcomponent S212. In a second variation, the step of implanting a femoralcomponent includes implanting a lateral femoral component S214. In athird variation, the step of implanting a femoral component includesimplanting a medial femoral component and implanting a lateral femoralcomponent. Alternatively, the step of implanting a femoral componentS210 includes implanting a full femoral component S216 that includes themedial and lateral femoral components, implanting a medial partialfemoral component S217, and/or implanting a lateral partial femoralcomponent S218. The medial femoral component preferably functions tobear load on the medial side of the knee and provide a bearing surfaceon the medial condyle, and is preferably adapted to cover and beintegrated into the medial femoral condyle of the patient. Similarly,the lateral femoral component preferably functions to bear load on thelateral side of the knee and provide a bearing surface on the lateralcondyle, and is preferably adapted to cover and be integrated into thelateral femoral condyle of the patient. The step of implanting a femoralcomponent 210 may include selecting a femoral component size from groupof available or supplied femoral components.

The step of placing a trial tibial component S220 preferably functionsto establish a placeholder tibial component for testing suitability offit. As shown in FIG. 15, in a first variation, the step of placing atrial tibial component S220 includes the step of selecting a trialmedial tibial component S222. The step of selecting a trial medialtibial component S222 preferably includes selecting a thickness from agroup of tibial component thicknesses S224, and selecting a size from agroup of tibial component planar coverage sizes S226. As shown in FIG.15, in a second variation, the step of selecting a trial tibialcomponent S220 includes selecting a trial lateral tibial component S232.The step of selecting a trial lateral tibial component S232 preferablyincludes selecting a thickness from a group of tibial componentthicknesses S234, and selecting a size from a group of tibial componentsizes S236. In a third variation, the step of selecting a trial tibialcomponent includes selecting a trial medial tibial component andselecting a trial lateral tibial component. The trial medial tibialcomponent is preferably adapted to cover and be integrated into themedial tibial plateau of the patient. Similarly, the trial lateraltibial component is preferably adapted to cover and be integrated intothe lateral tibial plateau of the patient. Alternatively, the step ofplacing a trial tibial component S220 may include placing a trial fulltibial component S233 on both the medial and lateral tibial plateaus.The step of placing a trial full tibial component preferably includesselecting a thickness from a group of tibial component thicknesses S235and selecting a size from a group of tibial component sizes S237. Thestep of placing a trial tibial component S220 may include the step ofcoupling the trial tibial component to a fixture that permits movementwithin a sagittal plane functions to prepare the trial tibial componentfor position adjustment. The step of coupling the trial tibial componentto a fixture preferably includes positioning the fixture on a tibia ofthe patient relative to the femoral component such that the femoralcomponent and the trial tibial component may articulate in knee motion.The trial tibial component is preferably removably coupled to thefixture. The fixture preferably allows movement of the trial tibialcomponent in an anterior-posterior direction.

Step S240, which includes adjusting at least one of tension of acruciate ligament and position of the trial tibial component, functionsto obtain the correct fit of the knee replacement system in the patient.S240 preferably includes at least one of: adjusting tension of theposterior cruciate ligament S242, adjusting tension of the anteriorcruciate ligament S244, adjusting the posterior position of the trialtibial component S250, and adjusting the anterior position of the trialtibial component S260. If the tension of the cruciate ligaments and theposition of the trial tibial component do not need to be adjusted, stepsS240 may be omitted.

The steps of adjusting tension of the posterior and anterior cruciateligaments function to set the PCL and ACL to an appropriate amount oftension to facilitate a full range of motion in flexion and extension.In embodiments in which medial and lateral tibial components will beimplanted in the patient, the PCL and ACL are preferably adjusted forboth the medial and lateral sides simultaneously, since the medial andlateral envelopes of functional motion are not independent. Anappropriately adjusted PCL preferably varies in tension throughout theknee range of motion, with tension beginning at 45 degrees of flexionand increasing with increasing flexion until maximum tension at 90degrees flexion (using a reference of a straight extended leg as having0 degrees of flexion). An appropriately adjusted ACL preferably hasadequate tension to allow the leg to externally rotate at fullextension, but without excessive tension that results in flexioncontracture (inability to actively or passively fully extend the leg).The step of adjusting tension of the PCL S242 may include checking forexcessive or insufficient PCL tension, reducing PCL tension tocompensate for excessive PCL tension, and/or increasing PCL tension tocompensate for insufficient PCL tension. Excessive or insufficienttension may be determined or tested by one or more of several ways. In afirst variation, excessive tension is evident when the posterior femoralcondyles migrate too far posteriorly with flexion, which may cause theposterior end of the trial tibial component to lift superiorly upwards.In a second variation, identifying the location of the tibiofemoralcontact area and comparing to an ideal or desired location may indicatewhether PCL tension is excessive, insufficient, or appropriate. Forexample, measuring displacement of the tibiofemoral contact arearelative to reference marks created on the trial tibial component, usingcontact film, or other electronic or visual means of locating thetibiofemoral contact area may provide a quantitative determination ofexcessive or insufficient tension. In a third variation, excessive orinsufficient tension may be determined by direct measure of tension inthe PCL such as with an electronic instrument. Insufficient tension maybe determined in a similar manner as excessive tension is determined.However, checking for excessive or insufficient tension may include anysuitable step. The step of reducing tension in the PCL preferablyincludes increasing the flexion space between the femur and tibia,replacing the trial femoral component with a smaller size, preferablywith a trial femoral component having a shorter anterior to posteriordimension (such as by 1-2 millimeters), although the trial tibialcomponent may be replaced by another trial tibial component that isadditionally and/or alternatively thinner, smaller in any suitabledimension, and/or any suitable shape to reduce the excessive tension inthe PCL. Increasing tension in the PCL preferably includes decreasingthe flexion space between the femur and tibia, such as by adding morematerial to the distal end of the femur, selecting a trial tibialcomponent that is thicker in the posterior portion, or selecting a trialtibial component having a smaller radius of curvature (e.g., smallerposterior radius of curvature 140 or 180). However, reducing orincreasing tension in the PCL may include any suitable step.

The step of adjusting tension of the ACL S244 may include checking forexcessive or insufficient ACL tension, reducing ACL tension tocompensate for excessive ACL tension, and/or increasing ACL tension tocompensate for insufficient ACL tension. Checking for excessive orinsufficient ACL tension may be one or more of several variations. Inone variation, excessive ACL tension may be determined by identifyingpresence of flexion contracture where the flexion space between thefemur and tibia is adequate and other collateral ligaments are balanced.In another variation, excessive or insufficient ACL tension may bedetermined by identifying that the leg is unable to passively externallyrotate during full extension to a certain amount of external rotation.The amount of external rotation may be measured with an electronicinstrument, visually, or any suitable means. Reducing ACL tension tocompensate for excessive ACL tension may include selecting a trialtibial component that has a thinner anterior portion and/or has a largerradius of curvature (e.g., larger anterior radius of curvature 142 or182). Increasing ACL tension to compensate for excessive ACL tension mayinclude selecting a trial tibial component that has a thicker anteriorportion and/or a smaller radius of curvature (e.g., smaller anteriorradius of curvature 142 or 182).

The step of adjusting the posterior position of the trial tibialcomponent S250 functions to adjust the posterior constraint of the trialtibial component to enable a natural functional envelope of motion,using the natural function of cruciate ligaments in a healthy knee as aguide. As shown in FIG. 16, in a first variation, the step of adjustingthe posterior position S250 includes adjusting the posterior position ofthe trial medial tibial component S252. As shown in FIG. 12A, the stepof adjusting the posterior position of the trial medial tibial componentS252 preferably includes simulating knee condition at onset of heelstrike S254 and adjusting the position of the trial medial tibialcomponent such that the ACL resists the simulated heel strike kneecondition S256. The step of simulating knee condition at onset of heelstrike S254 preferably includes extending the leg of the patient,anteriorly displacing the tibia relative to the femur, and externallyrotating the tibia. Exercising the tibia in this manner functions tosimulate knee conditions at onset of heel strike during walking, whichis when the anterior cruciate ligament (ACL) is normally at maximumtension in a healthy knee. In a second variation, the step of adjustingthe posterior position S250 includes adjusting the posterior position ofthe trial lateral tibial component S257. As shown in FIG. 12C, the stepof adjusting the posterior position of the trial lateral tibialcomponent S257 preferably includes simulating knee condition during deepflexion S258 and adjusting the position of the trial lateral tibialcomponent such that the PCL and/or ACL allows simulated deep flexionknee condition S259. The step of simulating knee condition during deepflexion S258 preferably includes flexing the leg and internally rotatingthe tibia. In the step of simulating knee condition during deep flexion,the leg is preferably flexed to approximately 145 degrees (relative to astraight-leg angle of zero degrees), but may alternatively be flexed toany suitable angle. Exercising the tibia in this manner functions tosimulate knee conditions during squatting, that is when the posteriorcruciate ligament (PCL) is normally slack enough to permit deep flexion.In a third variation, the step of adjusting the posterior position S250includes adjusting the posterior position of the trial medial tibialcomponent and adjusting the posterior position of the trial lateraltibial component, in which the steps of adjusting the posteriorpositions of the trial medial tibial component and the trial lateraltibial component are preferably identical to those of the first andsecond variations, respectively. If the adjusting steps as described arenot possible, the method is preferably repeated, beginning with the stepof selecting a trial tibial component.

The step of adjusting the anterior position of the trial tibialcomponent S260 functions to adjust the anterior constraint of the trialtibial component to enable a natural functional envelope of motion,using the natural function of cruciate ligaments in a healthy knee as aguide. As shown in FIGS. 12B and 17, in a first variation, the step ofadjusting the anterior position S260 includes adjusting the anteriorposition of the trial medial tibial component S262. The step ofadjusting the anterior position of the trial medial tibial componentS262 preferably includes simulating knee condition during onset of toeoff during walking S264 and adjusting the position of the trial medialtibial component such that the PCL resists the simulated toe off kneecondition S266. The step of simulating knee condition at toe off onsetS264 preferably includes flexing the leg, posteriorly displacing thetibia relative to the femur, and internally rotating the tibia.Exercising the tibia in this manner functions to simulate kneeconditions at onset of toe off during walking, which is when the PCL isnormally at a maximum tension in a healthy knee. In a second variation,the step of adjusting the anterior position S260 includes adjusting theanterior position of the trial lateral tibial component S267. The stepof adjusting the anterior position of the trial lateral tibial componentS267 preferably includes simulating knee condition during onset of toeoff during walking S268 and adjusting the position of the trial lateraltibial component such that the PCL resists the simulated toe off kneecondition S269. The step of simulating knee condition S268 and adjustingthe position of the trial lateral tibial component S269 are preferablysimilar to steps S264 and S266, respectively, of adjusting the anteriorposition of the trial medial tibial component S262. In a thirdvariation, the step of adjusting the anterior position includesadjusting the anterior position of the trial medial tibial component andadjusting the anterior position of the trial lateral tibial component,in which the steps of adjusting the anterior positions of the trialmedial tibial component and the trial lateral tibial component arepreferably identical to those of the first and second variations,respectively.

Step S270, which includes verifying appropriate cruciate ligamenttension and trial tibial component position, preferably includes stepssimilar to those for checking for excessive or insufficient tension ofthe PCL, checking for excessive or insufficient tension of the ACL,simulating heel strike onset during adjustment of the posterior positionof the trial medial tibial component, and simulating the knee conditionin deep flexion during adjustment of the anterior position of the triallateral tibial component.

The step of marking the position of the trial tibial component S280functions to record the optimum position of the trial tibial componentbased on the adjustments in position of the trial tibial component. Thestep of marking the position may be performed with biocompatible ink, aphotograph, an etching in tissue, or any suitable process.Alternatively, the position may be recorded with a photograph or otherrecording equipment.

The step of implanting a tibial component in the patient S290 based onthe marked position is preferably similar to the step of implanting afemoral component in the patient. In a first variation, the step ofimplanting a tibial component S290 includes implanting a medial tibialcomponent on the medial tibial plateau of the leg S292. In a secondvariation, the step of implanting a tibial component S290 includesimplanting a lateral tibial component on the lateral tibial plateau ofthe leg S294. In a third variation, the step of implanting a tibialcomponent includes implanting a full tibial component S296 that includesa medial tibial portion and a lateral tibial portion. In a fourthvariation, the step of implanting a tibial component includes implantinga medial tibial component and implanting a lateral tibial component. Themedial tibial component preferably functions to bear load on the medialside of the knee, and is preferably adapted to cover and be integratedinto the medial tibial plateau of the patient. Similarly, the lateraltibial component preferably functions to bear load on the lateral sideof the knee, and is preferably adapted to cover and be integrated intothe lateral tibial plateau of the patient.

The method may further include the step of repeating at least a portionof the method S238 if the performing at least one of the steps ofadjusting the tension of the PCL S282, adjusting the tension of the ACLS284, adjusting the posterior position S250 and adjusting the anteriorposition S260 are prevented by the trial tibial component size. Forexample, the steps of placing a trial tibial component S220 (includingselecting a trial tibial component), adjusting the posterior positionS250, and adjusting the anterior position S260 may be repeated untilboth adjusting steps S250 and S260 are successful.

Alternative versions of the method include the steps of adjusting theposterior position and adjusting the anterior position performed in anycombination and/or permutation, or simultaneously. As an example,adjusting the anterior position may be performed before adjusting theposterior position. As another example, the steps of adjusting theposterior position and adjusting the anterior position may be performedsimultaneously, by performing their substeps the following order:adjusting the posterior position of the trial medial tibial component,adjusting the anterior position of the trial medial tibial component,adjusting the posterior position of the trial lateral tibial component,and adjusting the anterior position of the trial medial tibialcomponent.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,”“connected to,” or “coupled to” another element or layer, it may bedirectly on, engaged, connected or coupled to the other element orlayer, or intervening elements or layers may be present. In contrast,when an element is referred to as being “directly on,” “directly engagedto,” “directly connected to,” or “directly coupled to” another elementor layer, there may be no intervening elements or layers present. Otherwords used to describe the relationship between elements should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” etc.). As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,”“lower,” “above,” “upper,” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the FIGS. Spatially relativeterms may be intended to encompass different orientations of the devicein use or operation in addition to the orientation depicted in the FIGS.For example, if the device in the FIGS. is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exampleterm “below” can encompass both an orientation of above and below. Thedevice may be otherwise oriented (rotated 90 degrees or at otherorientations) and the spatially relative descriptors used hereininterpreted accordingly.

What is claimed is:
 1. A method of supplying a knee replacement systemfor implantation in a patient, comprising the steps of: providing a setof multiple medial femoral components, each having a medial femoralarticulating surface that is scaled to a distinct medial femoral scalingfactor; providing a set of multiple lateral femoral components, eachhaving a lateral femoral articulating surface that is scaled to adistinct lateral femoral scaling factor; providing a set of multiplefull femoral components, each having a medial femoral portion and alateral femoral portion, wherein the medial femoral portion has a medialfemoral articulating portion that is scaled to a distinct medial femoralportion scaling factor and the lateral femoral portion has a lateralfemoral articulating portion that is scaled to a distinct lateralfemoral portion scaling factor; providing a set of multiple medialtibial components, each having a distinct thickness and a medial tibialarticulating surface that articulates with the medial femoralarticulating surface and is scaled to a distinct medial tibial scalingfactor; providing a set of multiple lateral tibial components, eachhaving a distinct thickness and a lateral tibial articulating surfacethat articulates with the lateral femoral articulating surface and isscaled to a distinct lateral tibial scaling factor; and providing a setof full tibial components, each having a medial tibial portion and alateral tibial portion, wherein the medial tibial portion has a medialtibial articulating portion that is scaled to a distinct medial tibialportion scaling factor and the lateral tibial portion has a lateraltibial articulating portion that is scaled to a distinct lateral tibialportion scaling factor.
 2. The method of claim 1, further comprisingselecting a medial femoral component from the set of multiple medialfemoral components and a medial tibial component from the set ofmultiple medial tibial components.
 3. The method of claim 1, furthercomprising selecting a lateral femoral component from the set ofmultiple lateral femoral components and a lateral tibial component fromthe set of multiple lateral tibial components.
 4. The method of claim 1,further comprising selecting a full femoral component from the set ofmultiple full femoral components.
 5. The method of claim 1, furthercomprising selecting a full tibial component from the set of multiplefull tibial components.
 6. A method of implanting a knee replacementsystem in a leg with a femur and a tibia of a patient, comprising thesteps of: implanting a femoral component onto a condyle of the femur inthe leg; placing a trial tibial component on a tibial plateau of thetibia in the patient; adjusting the tension of a posterior cruciateligament; adjusting the tension of an anterior cruciate ligament;adjusting the posterior position of the trial tibial component;simulating knee condition at toe off onset during walking; adjusting theanterior position of the trial tibial component such that the posteriorcruciate ligament in the leg resists the simulated toe off kneecondition; marking a position of the trial tibial component at theadjusted posterior and anterior positions; and implanting a tibialcomponent onto the tibial plateau in the patient in the marked positionthat articulates with the femoral component.
 7. The method of claim 6,wherein the step of placing a trial tibial component includes selectinga trial tibial component size based on at least one of thickness andplanar size of the trial tibial component.
 8. The method of claim 7,further comprising the step of repeating the step of selecting the trialtibial component size if performing at least one of the steps ofadjusting the posterior cruciate ligament and adjusting the anteriorcruciate ligament is prevented by the trial tibial component size. 9.The method of claim 7, further comprising the step of repeating the stepof selecting the trial tibial component size if performing at least oneof the steps of adjusting the posterior position and adjusting theanterior position is prevented by the trial tibial component size. 10.The method of claim 6, wherein the step of implanting a femoralcomponent includes implanting a medial femoral component onto a medialcondyle of the femur; wherein the step of placing a trial tibialcomponent includes placing a trial medial tibial component on a medialtibial plateau on the tibia; and wherein the step of implanting a tibialcomponent includes implanting a medial tibial component onto the medialtibial plateau.
 11. The method of claim 10, further comprising the stepof simulating knee condition at heel strike onset during walking,wherein the step of adjusting the posterior position includes adjustingthe posterior position of the trial medial tibial component such that aanterior cruciate ligament in the leg resists the simulated heel strikeknee condition.
 12. The method of claim 11, wherein the step ofsimulating knee condition at heel strike onset includes: extending theleg of the patient, anteriorly displacing the tibia relative to thefemur, and externally rotating the tibia.
 13. The method of claim 6,wherein the step of implanting a femoral component includes implanting alateral femoral component onto a lateral condyle of a femur; wherein thestep of placing a trial tibial component includes placing a triallateral tibial component on a lateral tibial plateau of the tibia; andwherein the step of implanting a tibial component includes implanting alateral tibial component onto the lateral tibial plateau.
 14. The methodof claim 8, further comprising the step of simulating knee conditionduring deep flexion, wherein the step of adjusting the posteriorposition includes adjusting the posterior position of the trial lateraltibial component such that at least one of an anterior cruciate ligamentand a posterior cruciate ligament in the leg allows the simulated deepflexion knee condition.
 15. The method of claim 14, wherein the step ofsimulating knee condition during deep flexion includes: flexing the legof the patient and internally rotating the tibia.
 16. The method ofclaim 6, wherein the step of adjusting the anterior position of thetrial tibial component includes adjusting the anterior position of thetrial tibial component such that a posterior cruciate ligament in theleg resists the simulated toe off knee condition.
 17. The method ofclaim 16, wherein the step of simulating knee condition at toe off onsetincludes: flexing the leg of the patient, posteriorly displacing thetibia relative to the femur, and internally rotating the tibia.